In 1995, biologists released fourteen wolves into Yellowstone National Park as a means of managing the critically high number of elk overgrazing within the reserve. It had been more than seventy years since wolves had resided in Yellowstone, and their reintroduction triggered an event known as a trophic cascade within the park’s ecosystem.

Through hunting, the wolves altered the feeding habits of the herds of elk, forcing them to avoid locations where they were easy prey. This divergence in grazing patterns allowed aspen and willow trees to regenerate, attracting bugs, which in turn lead to various bird species moving in. Shortly after the birds arrived, beavers returned to the area, building dams that provided shelter for otters and reptiles.

In addition to hunting elk, the wolves also killed off much of the coyote population, leading to an increase in the number of rabbits and mice who called Yellowstone home. This…